1. Field of the Invention
The present invention relates to a method of producing a vacuum container by using anode-coupling.
2. Description of the Related Art
FIG. 3 shows an example of a vacuum container schematically in cross-section. The vacuum container 1 shown in FIG. 3 comprises a base layer (e.g., glass layer) 2, a semiconductor layer (e.g., silicon layer) 3, and a lid layer (e.g., glass layer) 4. The base layer 2, the semiconductor layer 3, and the lid layer 4 are laminated and integrated sequentially in that order to produce a laminate 5. Concavities 2a and 4a are formed in the base layer 2 and the lid layer 4 in the positions thereof opposed to each other through the semiconductor layer 3. These concavities 2a and 4a form a vacuum cavity 6 inside the laminate 5.
A vibrator 7, for example, obtained by processing the semiconductor substrate constituting the semiconductor layers 3 is received in the vacuum cavity 6. The vibrator 7, received and disposed in the vacuum cavity 6, can be satisfactorily vibrated without suffering no damping by air.
FIG. 4 is a perspective view showing an example of the semiconductor layer 3, together with the base layer 2. The semiconductor layer 3 has a vibrator formed by processing the semiconductor substrate. The semiconductor layer 3 shown in FIG. 4 is formed by using a technique such as etching or the like. A sensor unit 8 containing the vibrator 7, and a sealing portion 9 surrounding the sensor unit 8 are formed in the semiconductor layer 3. The sealing portion 9 is sandwiched between the base layer 2 and the lid layer 4 from the upper and lower sides thereof shown in FIG. 4, respectively. The sealing portion is anode-coupled to the base layer 2 and the lid layer, respectively. Thus, the sealing portion 9 air-tightly seals the vacuum cavity 6 for containing the sensor unit 8.
The sensor unit 8 shown in FIG. 4, which constitutes an angular velocity sensor, comprises the quadrangular vibrator 7, vibrator supporting fixing portions 10 (10a, 10b, 10c, and 10d), electrode supporting-fixing portions 11 (11a and 11b), a detection electrode pad forming portion 12, beams 13 (13a, 13b, 13c, and 13d), interdigital movable electrodes 14 (14a and 14b), and interdigital fixed electrodes 15 (15a and 15b).
The vibrator supporting fixing portions 10 (10a, 10b, 10c, and 10d), the electrode supporting-fixing portions 11 (11a and 11b), and the detection electrode pad forming portion 12 are anode-coupled and fixed to the base layer 2 and the lid layer 4. The vibrator 7 is connected to and is communicated with the vibrator supporting fixing portions 10 (10a, 10b, 10c, and 10d) via the beams 13 (13a, 13b, 13c, and 13d), respectively. Moreover, the interdigital movable electrodes 14 (14a and 14b) are formed so as to protrude from the ends of the vibrator 7 in the X-direction in FIG. 4. The interdigital fixed electrodes 15 (15a and 15b) are formed so as to extend from the electrode supporting-fixing portions 11 (11a and 11b) in the X-direction in such a manner as to mesh with the interdigital movable electrodes 14 at an interval from the interdigital movable electrodes 14.
The concavities 2a and 4a, shown in FIG. 3, are formed in the base layer 2 and the lid layer 4 in the positions thereof which are opposed to the area of the semiconductor layer 3 in which the vibrator 7, the beams 13 (13a, 13b, 13c, and 13d), and the interdigital movable electrodes 14 (14a and 14b) are formed. In the concavities 2a and 2b, the vibrator 7, the beams 13 (13a, 13b, 13c, and 13d), and the interdigital movable electrodes 14 (14a and 14b) are movably lifted from the base layer 2 and the lid layer 4.
Electrode pads (not shown), which are metal films, are formed on the upper faces of the vibrator supporting fixing portions 10 (10a, 10b, 10c, and 10d), the electrode supporting-fixing portions 11 (11a and 11b), and the detection electrode pad forming portion 12, respectively. Perforations are formed in the lid layer 4 in the positions thereof opposed to the electrode pads, respectively. Thus, the electrode pads are exposed to the exterior, and can be electrically connected to an external circuit by wire-bonding or the like.
A detection electrode (not shown) is formed on the bottom of the concavity 2a of the base layer 2 in the position thereof opposed to the vibrator 7 at an interval therefrom. Moreover, a wiring pattern 16 for connecting the detection electrode and the detection electrode pad forming portion 12 to each other is formed on the base layer 2.
Referring to the sensor unit 8 shown in FIG. 4, when an AC current for driving is applied from the external circuit to the fixed electrodes 15a and 15b, for example, the electrostatic forces between the fixed electrode 15a and the movable electrode 14a and that between the fixed electrode 15b and the movable electrode 14b are changed depending on the above-mentioned AC voltage, so that the vibrator 7 is driven and vibrated in the X-direction shown in FIG. 4. If the vibrator 7 is rotated on the Y-axis while it is being driven and vibrated as described above, a Coriolis force is generated in the Z-direction. The Coriolis force is added to the vibrator 7, so that the vibrator 7 is vibrated in the Z-direction to be detected.
The vibration of the vibrator 7 in the Z-direction changes the interval between the vibrator 7 and the detection electrode to change, so that the electrostatic capacity between the vibrator 7 and the detection electrode is changed. The change in the electrostatic capacity is output from the detection electrode to the exterior via the wiring pattern 16 and the electrode pad. The angular velocity or the like of the rotation of the vibrator 7 on the Y-axis can be determined based on the detected value.
Referring to a process of producing the vacuum container 1 containing the vibrator 7 (sensor unit 8) shown in FIG. 4, for example, a base for forming a plurality of the base layers 2, a semiconductor substrate for forming a plurality of the semiconductor layers 3, and a lid material for forming a plurality of the lid layers 4 are sequentially laminated and integrated to produce a laminate. The laminate is divided into the areas for forming the vacuum containers, which are separated into the individual vacuum containers. Hereinafter, an example of the process of producing the vacuum container 1 will be described in detail with reference to FIGS. 5A to 5F. FIGS. 5A to 5F show the site corresponding to the part of the vacuum container taken along line Axe2x80x94A in FIG. 4, respectively.
First, a base 20 for forming a plurality of the base layers 2 is prepared as shown in FIG. 5A. The concavities 2a are formed in the predetermined areas of the base 20 for forming the respective base layers 2. The detection electrode and the wiring pattern 16 are formed on the inner wall of each concavity 2a by a technique such as sputtering or the like. Then, a semiconductor substrate 21 is placed on the upper side of the base 20 in such a manner as to close the openings of the concavities 2a, as shown in FIG. 5B. The base 20 and the semiconductor substrate 21 are anode-coupled to each other. Then, the semiconductor substrate 21 is surface-ground till a predetermined thickness. Thereafter, the upper side of the semiconductor substrate 21 is polished to have a mirror-like surface as shown in FIG. 5C.
After this, the semiconductor substrate 21 is processed by using such a technique as etching, photolithography, or the like, as shown in FIG. 5D. The semiconductor substrate 21 is processed to form the semiconductor layers 3 of a plurality of the vacuum containers 1. In particular, by processing the semiconductor substrate 21, the patterns shown in FIG. 4 are formed in the areas of the semiconductor substrate 21 for forming the semiconductor layers, respectively. Electrode pads are formed on the upper side of the semiconductor substrate 21 by a thin-film formation technique such as sputtering or the like.
Thereafter, a lid material 22 is placed on the upper side of the semiconductor substrate 21 in a vacuum chamber where vacuum-exhausting is being carried out as shown in FIG. 5E. The lid material 22 is processed to form the lid layers 4 of the plurality of the vacuum containers. Previously, the concavities 4a and a plurality of the perforations (not shown) are formed in the areas of the lid material 22 for forming the lid layers, respectively. Referring to the above-described placement of the lid material 22 on the upper side of the semiconductor substrate 21, the lid material 22 is positioned in such a manner that the concavities 4a are opposed to the corresponding vibrators 7 at an interval, and moreover, the positions of the plurality of the perforations coincide with those of the electrode pads formed on the vibrator supporting fixing portions 10 (10a, 10b, 10c, and 10d), the electrode supporting-fixing portions 11 (11a and 11b), and the detection electrode pad forming portion 12, respectively. Thus, the lid material 22 is placed on the upper side of the semiconductor substrate 21.
Succeedingly, an electrode plate 24 electrically connected to voltage-applying means 25 is mounted onto the upper side of the lid material 22, and the semiconductor substrate 21 is electrically connected to the voltage-applying means 25 in the above-mentioned vacuum chamber. After this, high voltage for anode-coupling is applied between the semiconductor substrate 21 and the electrode plate 24 to anode-couple the lid material 22 and the semiconductor substrate 21 to each other. Thus, the laminate in which the base 20, the semiconductor substrate 21, and the lid material 22 are laminated and integrated is formed as shown in FIG. 5F. The vacuum cavities 6 containing the vibrators 7 are formed and air-tightly sealed in the vacuum container formation areas of the laminate, respectively.
After this, the laminate comprising the base 20, the semiconductor substrate 21, and the lid material 22 are cut along predetermined dicing lines to be divided and separated into the individual vacuum containers. Thus, the vacuum container 1 can be produced in the above-described manner.
However, when the lid material 22 is anode-coupled to the upper side of the semiconductor substrate 21 according to the above-described process of producing the vacuum container 1, undesirable gas is evolved in the portions of the semiconductor substrate 21 and the lid material 22 which are anode-coupled to each other. The gas flows into the vacuum cavity 6. Thus, the vacuum cavity 6 is air-tightly sealed while the flown undesirable gas remains in the vacuum cavity 6. Therefore, problematically, a desirable vacuum condition in the vacuum cavity 6 can be obtained with difficulty, due to the undesirable gas.
Moreover, the evolution amount of the undesirable gas varies, so that the vacuum degrees of the vacuum cavities 6 become different from each other depending on the vacuum containers 1. Accordingly, when the vibrators 7 constituting the angular velocity sensors shown in FIG. 4 are contained in the vacuum cavities 6 of the vacuum containers 1, for example, the vibration states of the vibrators 7 become different from each other depending on the vacuum containers 1. Accordingly, the performances of the angular velocity sensors become different from each other, and so forth. Thus, a problem arises in that the qualities of products are scattered.
To solve these problems, a technique for preventing deterioration of the vacuum degree of the vacuum cavity 6 and scattering of the vacuum degree, by which a gas adsorptive substance, in addition to the vibrator 7, is contained in the vacuum cavity 6 to adsorb the undesirable gas, has been proposed. However, the gas adsorptive substance needs to be placed in each of the vacuum cavities 6. A problem arises in that it is troublesome and takes much time to carry out the technique. Moreover, the vacuum cavities 6 are required to be enlarged in order to contain the gas adsorptive substance. Thus, inevitably, a problem occurs in that the sizes of the vacuum containers 1 are increased.
To solve the above-described problems, the present invention has been devised. It is an object of the present invention to provide a method of producing a vacuum container in which the vacuum cavity can be easily controlled so as to have a desirable vacuum state, and which is small in size.
To achieve the above-described object, according to the present invention, there is provided a method of producing a vacuum container which has a vacuum cavity formed inside a laminate including a base layer, a semiconductor layer, and a lid layer which comprises the steps: coupling a semiconductor substrate to the upper side of a base; anode-coupling a lid material to the upper side of the semiconductor substrate to form a laminate; and dividing and separating the laminate into predetermined individual areas; the lid material being placed on the upper side of the semiconductor substrate after the semiconductor substrate is coupled to the base, the semiconductor substrate and the lid material being anode-coupled to each other in a spot pattern, and succeedingly, the semiconductor substrate and the lid material being entirely anode-coupled to each other.
Preferably, the body of the base and the semiconductor substrate coupled to each other and the lid material are arranged in the atmosphere, the semiconductor substrate and the lid material are anode-coupled to each other in a spot pattern, and succeedingly, the semiconductor substrate and the lid material are entirely anode-coupled to each other in a vacuum in which vacuum-exhausting is carried out.
As described above, after the semiconductor substrate and the lid material are anode-coupled to each other in a spot pattern, the semiconductor substrate and the lid material are entirely anode-coupled to each other. By anode-coupling the semiconductor substrate and the lid material in plural steps, the vacuum degree of the vacuum cavity of the vacuum container can be desirably enhanced compared to that obtained by entirely anode-coupling the semiconductor substrate to the lid material at one time as conventionally carried out.